\documentclass{article}
\usepackage[svgnames]{xcolor}
\usepackage{tikz}

\pgfsetxvec {\pgfpoint {10pt }{0}}
\pgfsetyvec {\pgfpoint {0}{10 pt}}

\begin{document}

\tikzset{
	box/.style={rectangle, rounded corners=5pt,
		    minimum width=50pt, minimum height=20pt,
		    inner sep=5pt, draw=Silver,fill=Lavender}
}
\begin{tikzpicture}
\node[box] (l0)at(0,0){15};
\node[box] (l1)at(8,0){12};
\node[box] (l2)at(16,0){27};
\draw[->] (l0)--(l1);
\draw[->] (l1)--(l2);
\node at(4,1) {link};
\node at(12,1) {link};
\draw[->](-0.2,0)--(6,0) node[right]{$x$};
\draw[->](0,-0.2)--(0,6) node[above]{$f(x)$};
\draw[domain=0:4]plot(\x,{0.1*exp(\x)})node[right]{$f(x)=\frac{1}{10}e^x$};
\end{tikzpicture}

\begin{tikzpicture}
\draw(0,0)--(2,0)--(2,2)--(0,0);
\draw[rounded corners](5,0)--(7,0)--(7,2)--(5,0);
\draw[rounded corners](8,0)--(10,0)--(10,2)--cycle;
\draw(3,3) circle(2);
\draw(3,3) ellipse(2 and 1);
\draw(10,5) arc(0:270:1);
\draw[help lines,step=5pt](4,-2)grid(7,2);
\fill[Wheat]circle(1);
\filldraw[draw=Silver,fill=Lavender](14,1)circle(1);
\shade (5,-2) rectangle (7,2);
\end{tikzpicture}
\end{document}
